The final episode of Lost in May was one of the world's great TV experiences – 59 countries either simulcast the show or showed it the same day. The epic fantasy adventure wound up after 121 hours of television, screened in 220 countries, with a two and a half hour special that pulled in 13.5 million viewers in the US alone. The series had always been a darling of the online world, so when its co-creator Damon Lindelof started talking about the internet when accepting an award, it seemed likely he would thank people for their dedication or explain how they had built the fan base. But no.

Instead, Lindelof read out messages posted on Twitter by fans. "My very first tweet," wrote one. "I started this account just to let you know how disappointed I am in you." Which was sad, obviously, but as nothing compared to: "Hey, douche! Instead of backpacking in Europe or whatever the fuck you're doing, how about you give me six years of my life back?"

Sitting back

Lindelof was comparatively lucky. The abuse he received came after his six seasons were done and he was sitting back counting the syndication cheques flooding in. Ash Atalla, the producer of The Office, The IT Crowd and Man Stroke Woman, had a slightly more in-your-face experience.

"If you want a weird experience, make a TV show and watch it with the live Twitter feed on the go," he says. "Honestly, two minutes in people are going 'This is shit. This is the worst thing I've ever seen. Fail.' You're going, 'Wow, we are minutes in here'. The ferocity of people's responses – but I suppose that's comedy. People never go into work and say 'Did you see that documentary on troubled teenagers? It was shit.'"

Atalla's private hell is rapidly becoming the norm for TV people. Research published last week by Thinkbox revealed that so-called 2screening – where viewers watch TV while chatting online – is increasingly commonplace. According to the research, 60% of people claim to concurrently watch TV and go online at least two or three times a week, with one in three people claiming to do so every day. Although a narrow majority of 2screeners were actually shopping while they watched, 44% used social networks such as Facebook and Twitter.

For creators of scripted shows, this can be a nightmare. "I love Twitter and have a lovely group that's really supportive," says Iain Morris, the co-creator of The Inbetweeners. "But I watched the first three episodes of series three from abroad so effectively watched them via Twitter and I found it crippling. It made me rethink the fundamentals of how TV is made. Over nine months you make hundreds of decisions – character, plot, jokes. You used to get a review the following day from someone who had seen the whole and had an opinion of that – broadly they liked it or didn't, and there were good bits or bad bits. Now you see every decision you made being torn apart in real time as it goes out and it can cripple you."

Morris, who is working on a film version of The Inbetweeners, says his approach to the new script has been affected. "I'm still trying to divorce the two," he explains. "I'm still getting tweets saying 'Could you make the characters a bit more like this?' And you want to say 'Look, we're not a covers band.'"

Given its effects on Atalla and Morris, could it be that social networking is damaging TV creativity? Not everyone thinks so: "Actually Twitter loves my shows, particularly Giles and Sue," says Daisy Goodwin, whose indie Silver River makes BBC2's Giles and Sue Live the Good Life. "The Twitter feed has convinced the BBC to commission another series, on the basis of how enthusiastic and how young the audience is – not to mention Giles Coren's huge gay following. Who knew?

"I think double screening enhances the viewing process. It is good news for producers because it brings back the watercooler element to TV, except that it is happening live. I know I am really loving a show like Downton Abbey when my fingers are not itching to press the Twitter button." Certainly there seems to be a difference between factual and scripted TV when it comes to facing the Twitterati. "Factual producers couldn't care less about what the viewers think unless it affects the ratings," one reality TV producer confides. "We're not as sensitive as scripted types. We certainly don't let the viewers influence our editorial. What you can do is create moments as a Twitter bomb – what used to be called car crash TV. If you drop in something mad early enough in the show you can see the swarm of tweets go up. It probably has a negligible effect on the actual viewing figures, but it creates a buzz, hits the papers the next day, keeps the broadcaster happy as their show is in the news and, seeing as we're all looking to monetise these days, gives you some online numbers you can look at making money out of."

Next day

For James Herring, the managing partner of Taylor Herring – the PR company handling The Apprentice – it's all about managing the two screens. "In the old days you'd send out a tape then read the reviews the next day," he says. "Now there's a constant unfolding critique of the show from the moment it starts, and you have to have a rota of people monitoring that. Twitter is usually harsher – it's people trying to sound like Caitlin Moran and Grace Dent – whilst Facebook is generally more positive with groups of friends discussing the shows they like.

"A few reviewers like to get the mood online before arriving at their own opinion, so what's said online is important. We have lists of the journalists and top 10 media buyers' various pages, which we keep an eye on as the show goes out – it's a powerful tool for us. TV companies can pay £20,000 for a focus group, but here you're getting it for free."

For the League of Gentlemen, Doctor Who and Sherlock writer-performer Mark Gatiss, the answer is simple – creatives should turn it off when their own stuff goes out: "It's like listening at a door – if you don't want to hear anything bad about yourself, don't do it," he says. "It enfranchises the lunatic fringe in a startling way, those people who used to write green ink letters to the BBC, but because it's on screen it looks real. I'm a recent convert to Twitter and I like using it, but if you watch it while your show goes out you will go mad."